Ultrasonic image processing method and system for displaying a composite image sequence of an artery segment
The invention relates to an ultrasonic image processing method for displaying a composite sequence of images of an artery segment with indication of blood flow velocity and wall movements in function of the cardiac cycle, comprising steps of forming, at a first rate, a first sequence of blood flow velocity color-coded images and forming, at a second rate, a second sequence of images with wall movement graphics. The invention also relates to an ultrasonic diagnostic imaging system for carrying out this method.
The invention is used in the field of medical echographic imaging, for providing cardiovascular diagnostic tools for non-invasive study of anomalies of arteries and notably of stenoses. A diagnostic criterion for a stenosis is an abrupt reduction of an artery diameter. Another criterion is the blood velocity in the stenosed zone. Therefore, the medical field has a need for non-invasive means for studying parameters related to arterial wall motion and to blood flow velocity in order to early diagnostic stenosed arteries.
A method for displaying a composite sequence of images of an artery segment with indication of color-coded blood flow velocity and arterial wall movement graphics in function of the cardiac cycle is already known from the PCT patent application No WO 99/25250. This method comprises steps of forming, at a first rate, a first sequence of blood flow velocity color-coded images and of forming, at a second rate, a second sequence of images with wall movement graphics and finally of superposing the first and second sequences by synchronizing markers of the starts of the cardiac cycles, previously measured for first and second sequences separately, using an external ECG device. To this end, the ECG measure means is to be applied to the patient in supplement to the ultrasonic measure means. The start and end points of the first and second sequences are further made to coincide by using calculation steps. Then, the composite image sequence is displayed.
As explained before, it is of importance that indications of the actual movements of the walls be available together with the blood flow velocity in order to diagnose stenoses or other diseases. A technical problem resides in the fact that processing a first set of data appropriate to provide arterial wall radial velocity together with processing a second set of data appropriate to provide either Doppler Imaging or CVI is difficult because said first and second sets of data are actually incompatible due to the respective velocities of arterial walls and blood flow, which are in the ratio of one to about fifty. It is the reason why the document cited as state of the art used a system based on supplementary ECG measurements in order to synchronize the first and second sets of data.
It is a purpose of the invention to provide an image processing method for synchronizing the two sequences of images that are formed from these two sets of data.
This problem is solved by means of a method as claimed in claim 1.
This method offers the advantage that the synchronization is performed using uniquely image processing. This method spares the patient to suffer supplementary ECG measure means and it spares the operator to perform supplementary ECG measures. This method also avoids inaccuracies that appear while making ultrasonic measures and ECG measures coincide. This method also offers the advantage that the arterial wall behavior is made clearly visible together with color-coded indications of the blood flow velocity. So, the physician may easily diagnose stenosis or arterial anomalies.
An ultrasonic diagnostic system having means for carrying out the method is claimed in claim 10, and constitutes a tool for non-invasive diagnostic of arterial wall anomalies.